[dart:io] Don't apply the namespace to the kernel service isolate

Change-Id: If29cb9c0202c8121f6076025fb3870d4f5721948
Reviewed-on: https://dart-review.googlesource.com/59903
Reviewed-by: Siva Annamalai <asiva@google.com>
Commit-Queue: Zach Anderson <zra@google.com>
diff --git a/runtime/bin/main.cc b/runtime/bin/main.cc
index 0348dbd..01e11b7 100644
--- a/runtime/bin/main.cc
+++ b/runtime/bin/main.cc
@@ -367,8 +367,10 @@
     CHECK_RESULT(result);
   }
 
+  const char* namespc =
+      Dart_IsKernelIsolate(isolate) ? NULL : Options::namespc();
   if (isolate_run_app_snapshot) {
-    result = DartUtils::SetupIOLibrary(Options::namespc(), script_uri,
+    result = DartUtils::SetupIOLibrary(namespc, script_uri,
                                        Options::exit_disabled());
     CHECK_RESULT(result);
     if (FLAG_support_service || !kDartPrecompiledRuntime) {
@@ -411,7 +413,7 @@
                        Dart_GetMainPortId(), Dart_Timeline_Event_Async_End, 0,
                        NULL, NULL);
 
-    result = DartUtils::SetupIOLibrary(Options::namespc(), script_uri,
+    result = DartUtils::SetupIOLibrary(namespc, script_uri,
                                        Options::exit_disabled());
     CHECK_RESULT(result);
 #else